The San Francisco Deputy Sheriffs' Association sent a letter Friday to Board of Supervisors members opposing a move to prohibit law enforcement from detaining undocumented immigrants suspected of committing crimes.

The organization, which represents those who oversee The City's jails, became the latest entity to join the percolating debate over a controversial federal program called Secure Communities, or S-Comm.

At issue is whether the Sheriff's Department should continue to honor immigration holds, or detainers, that are ordered by U.S. Immigration and Customs Enforcement. Under the federal program, the fingerprints of those arrested by local law enforcement agencies are reviewed by ICE officials who can request that a person be held for up to 48 hours so suspects can be picked up for deportation.

The current Sheriff's Department policy states that those who are in custody on suspicion of a serious and violent felony, such as murder or rape, or who have previous convictions for serious felonies can be detained for up to 24 hours when they are otherwise eligible for release. Last year, 542 people were turned over to ICE under that policy.

But detaining anyone at ICE's request could be prohibited Tuesday if the Board of Supervisors approves legislation introduced by Supervisor John Avalos.

Police Chief Greg Suhr has said the power to honor the detainer requests for the most violent offenders should remain at the discretion of the sheriff. Otherwise, he has said, San Francisco could become a destination for criminals, and those who would be deported under current policy could instead end up on the streets committing more crimes.

Meanwhile, domestic violence activists and District Attorney George Gascón have come out strongly in favor of the legislation, providing Avalos with significant political weight. Sheriff Ross Mirkarimi also backs the proposal.

Supporters say the detainers violate the right to due process and erode the vital trust between the undocumented immigrant community and law enforcement, which is seen as vital to ensuring that crimes are reported and witnesses cooperate.

But while Avalos has at least eight votes on the 11-member board, which is enough to overturn a mayoral veto, he said Friday that Mayor's Office staff are "trying every trick in the bag to try and pick off my votes."

Mayor Ed Lee supports the fundamental principles of the legislation, but has public safety concerns he hopes are addressed Tuesday by board members, mayoral spokeswoman Christine Falvey said.

Avalos said if any "carve-outs" are made against his wishes then the title of the legislation, Due Process for All, should also be changed to "Due Process for Some," which he said is a direct affront to the U.S. Constitution.